Liquid crystal display devices are used as display devices in various information-processing devices, including mobile phones, PDAs (Personal Digital Assistants), ATMs (Automatic Teller Machines) and personal computers. In recent years, liquid crystal display devices wide in visible range have been put into practical use.
As such a liquid crystal display device, there has been commonly known a device equipped inside with an optical device for adjusting the outgoing direction of light input from the back side of the device, and including a backlight for uniformly emitting light toward this optical device and a liquid crystal display for displaying images.
Various light distribution characteristics have been required of the liquid crystal display device as the device is increased in display size and made multipurpose.
From the viewpoint of information leakage in particular, there are requirements of, for example, restricting a visible range so as not to be peered into by others and preventing light from being emitted in unwanted directions. As an optical device configured to meet these requirements, an optical film capable of restricting the visible range (or the range of emission) of a display has been proposed and put into practical use.
In a liquid crystal display device that employs the above-mentioned optical film, however, the optical film has to be detached each time the display is simultaneously viewed from a plurality of directions. This imposes cumbersome procedures on users and incurs time loss. There is therefore a growing demand for realizing the states of the display device being in a wide-visible range and a narrow-visible range at any point of time, without having to take the time to detach the optical film.
Accordingly, an optical device capable of switching the visible range of the display between a wide-field mode and a narrow-field mode has been proposed in response to such requirements.
Examples of such an optical device, as illustrated in the cross-sectional view of FIG. 35, include an optical device 410 configured such that a transparent photopolymer layer is exposed and developed using two oppositely-disposed transparent substrates 421 and 422 and heat-hardened to form light transmissive regions 440 with gaps between them, and each electrophoretic element 460 is disposed in gaps between these light transmissive regions 440. Here, transparent conductive films 451 and 452 are formed between the transparent substrate 421 and the light transmissive regions 440 and between the transparent substrate 422 and the light transmissive regions 440, respectively.
The optical device 410 in which each electrophoretic element 460 is disposed in gaps between high-aspect ratio light transmissive regions 440 planarly and independently laid out on the transparent substrate 421 as described above is configured such that the dispersion state of the electrophoretic elements 460 is controlled by externally applying electric fields through the transparent conductive films 451 and 452, thereby optionally realizing two states, i.e., a narrow-field mode and a wide-field mode, according to the emission state of light (incident light) 750.
That is, the externally-applied electric fields are adjusted to optionally switch between the narrow-field mode illustrated in FIG. 35A and the wide-field mode illustrated in FIG. 35B, thereby realizing the two emission states of light 750.
Such a technology as described in, for example, Patent Document 1 or Patent Document 2 is known as a technology of applying electrophoretic elements.
The optical device 510 disclosed in Patent Document 1, as shown in the cross-sectional view illustrated in FIG. 36, includes a transparent substrate 521, a transparent conductive film 551 formed on a surface of the transparent substrate 521, a plurality of light transmissive regions 540 formed on an upper surface 551a of this transparent conductive film 551 at a distance from one another, and electrophoretic elements 560 disposed among these light transmissive regions 540, and another transparent substrate 522 provided with another transparent conductive film 552 on the light transmissive region 540-side surface of the transparent substrate 522 is disposed on the upper surface 540a side of the light transmissive regions 540.
The electrophoretic display device 610, as shown in the cross-sectional view illustrated in FIG. 37, disclosed in Patent Document 2 includes concave portions 620A formed in a base material 620, an aluminum electrode 650 provided on the bottom surface of each concave portion 620A, an electrophoretic element 660 disposed in each concave portion 620A, a transparent electrode 651 provided on the upper surface of the base material 620, an adhesive agent 690 provided on the upper surface of this transparent electrode 651, and a transparent base material 621 provided on the upper surface of this adhesive agent 690.
Patent Document 1: U.S. Pat. No. 7,751,667
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2002-122891